The Earth’s complex and dynamic magnetic field is vital for the survival of all life forms, protecting the planet from cosmic radiation and charged particles coming from the sun.
This field originates from an ocean of molten liquid iron that forms the Earth's outer core at a depth of about 3000 km beneath our feet.
This rotating ocean of iron, much like a bicycle alternator, creates electric currents, which in turn generate the planet's protective electromagnetic field. However, the precise processes that generate this magnetic field are more complex and still require further investigation.
For example, in the Southern Hemisphere, the magnetic field is particularly strong at one point, and in the Northern Hemisphere there are two such points – one around Canada and the other around Siberia.
Scientists are gaining deeper insights into the planet's magnetism thanks to data from a set of three identical satellites launched in 2013, which measure magnetic signals separately from Earth's core, mantle, crust, and oceans, as well as the planet's outer atmospheric layers.
Now, after tracking 11 years of magnetic field measurements from these satellites, scientists have discovered that the weak region of Earth’s magnetic field over the South Atlantic – known as the “South Atlantic Anomaly” – has also expanded by an area nearly half the size of continental Europe since 2014, according to a new study published in the journal Hysics of the Earth and Planetary Interiors.
Chris Finlay, lead author of the study from the Technical University of Denmark, says: "The South Atlantic Anomaly is not just one block. It changes differently towards Africa compared to when it is near South America. There is something special happening in this region that is causing the field to weaken more sharply."
Scientists link this distortion in Earth's magnetic field to strange patterns at the boundary between Earth's liquid outer core and its rocky mantle.
Dr. Finlay explains: "We normally expect to see magnetic field lines coming out of the core in the Southern Hemisphere, but under the South Atlantic Anomaly we see unexpected regions where the magnetic field returns to the core instead of coming out of it."
He adds: "Thanks to Swarm satellite data, we can see one of these areas moving westward over Africa, which contributes to weakening the South Atlantic Anomaly in this region."
The latest satellite data indicates that the magnetic field over Siberia has become stronger, while it has weakened over Canada.
Scientists say this shift is important for satellite navigation systems, which are affected by the dance between these two regions of strong magnetic field.
Scientists warn that this could be a key factor in determining the radiation dose to which satellites in low Earth orbit are exposed. Spacecraft and astronauts, including those aboard the International Space Station, entering the South Atlantic Ocean could also be exposed to increased radiation.